Achievements
Complete each of the following achievements below to get the allotted gamerscore:

Amateur Collector (40) - Collect 66% Souvenir Mugs in the game.
Art Collector (50) - Collect 100% of Coloring Book Pages in the game.
For the Fridge (30) - Collect 33% of Coloring Book Pages in the game.
Glorious Liege (80) - Complete the game in Grimm Difficulty.
Hail to the King! (60) - Complete all 20 missions of the game for the first time in any difficulty.
Ice Dragon Tamer (30) - Defeat the Ice Dragon. (Normal Difficulty or higher).
Master Collector (50) - Collect all Souvenir Mugs in the game.
Music Critic (30) - Defeat Captain Hook. (Normal Difficulty or higher).
Novice Collector (30) - Collect 33% Souvenir Mugs in the game.
Ogre Smash! (30) - Use Fairy Dust Attack 50 times with any character.
Questing Fiend (50) - Complete 66% of the Challenge Quests in the game.
Questing Ogre (80) - Complete all the Challenge Quests in the game.
Questing Rookie (40) - Complete 33% of the Challenge Quests in the game.
Spoon Fed Ogre (30) - Complete the game in Charming Difficulty.
Super Ogre (30) - Use Super Ogre Power 5 times with Shrek or Fiona.
Super Ogre Power Extreme (60) - Use Super Ogre Power 10 times with any character.
Survivor Shrek (60) - Achieve a Perfect on every level. (Normal difficulty or higher).
The Collector (60) - Complete all of The Collector series of quests.
The Finisher (50) - Perform 100 finishing moves.
The Juggler (40) - Launch 50 Enemies into the air then catch them with Shrek.
Upstaged Charming (30) - Defeat Prince Charming. (Normal Difficulty or higher).
Upstart Artist (40) - Collect 66% of Coloring Book Pages in the game.

Unlock Charming and Grimm difficulties
You can purchase the Charming and Grimm difficulties in the Gift Shop at the main menu: